Link to issue number:

Fixes #12920

Summary of the issue:

Adobe Acrobat / Reader 64 bit crashes when NVDA renders a virtualBuffer for PDF content.
There are two reasons for this:

1. Adobe's IAccID custom interface has been changed so that specifically on 64 bit builds, the ID argument is now 64 bit wide instead of 32 bit. This meant that NVDA was using the wrong data type and wrong call signature for IAccID::get_accID, and therefore Acrobat / Reader was trying to write a 64 bit value in to the space that could only hold 32 bits, causing a buffer overrun.
2. Adobe Acrobat / Reader's accID values, including the MSAA child IDs used for IAccessible::get_accChild and AccessibleObjectFromEvent were 64 bit wide, though MSAA only supports 32 bit values. This would cause invalid and truncated values to be used for child IDs, in many cases causing a crash.

Adobe has addressed point 2 in Adobe Acrobat / Reader beta versions and will be in a stable build in the near future.
But NVDA needs to address point 1 in its own code.

Description of user facing changes

Using a version of Adobe Acrobat / Reader with the required fixes on adobe's side, along with this PR in NVDA, the crash is avoided.

Description of development approach

miscDeps has been updated to contain the newest version of acrobatAccess.idl from the Adobe Acrobat SDK.
The adobeAcrobat vbufBackend getAccID method has been changed to fetch the out param of IAccID::get_accID with a LONG_PRT which will be 64 bit wide on 64 bit Acrobat / Reader, and 32 bit wide on 32 bit Acrobat / Reader. The value is then static casted to long when returned. As Acrobat always uses 32 bit accID vlaues, no information will be lost in the conversion.

Testing strategy:

Opened multiple pdf documents in Adobe Acrobat / Reader while running NVDA. Ensured that Acrobat / Reader did not crash and that the pdf could be read with the arrow keys.

Known issues with pull request:

None known.

Change log entries:

New features
Changes
Bug fixes

• Adobe Acrobat / Reader 64 bit will no longer crash when reading a PDF document. (NVDA does not work with Adobe reader DC 64 bit #12920)
  • Note that the most up to date version of Adobe Acrobat / Reader is also required to avoid the crash.
    For Developers

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English